The present invention involves a refrigeration control system for controlling the operation of refrigeration equipment to insure efficient operation thereof under a sophisticated control of critical temperature and pressure parameters.
In recent years numerous technological advances have been made for optimizing the energy use of a refrigeration system through the use of electronic controls. One such system is disclosed in assignee's U.S. Pat. No. 4,478,051 to Ibrahim. In that patent an electronically controlled expansion valve is actuated under the control of a series of temperature and pressure determinations to secure efficient operation and particularly to maintain the temperature of the refrigerant discharged from the evaporator coil above the saturation temperature. The present invention constitutes an improved control system which incorporates multiple temperature and pressure control concepts capable of providing highly effective and energy efficient control of refrigerated display cases and systems.
Other electronic control systems for refrigeration systems are disclosed in U.S. Pat. Nos. 3,872,685 to Matthis, 4,102,150 and 4,112,703 to Kountz, 4,129,995 to Usami and 2,614,393 to Schulz et al.
The Matthis patent disclosed an electronically controlled expansion valve wherein the temperature at the outlet of the refrigeration air conduit is measured and compared with a preselected temperature for controlling the operation of the expansion valve.
The two patents to Kountz disclose systems for controlling air conditioning refrigeration systems used in automobiles. In the first of these patents the temperature along the discharge line from the evaporator coil is measured and the temperature within the space being air conditioned is measured and each of these temperatures is compared to a set temperature and in response to such comparison output signals are provided for controlling the operation of a solenoid operated control valve located in a by-pass line around the compressor for controlling the crankcase pressure within the compressor. In the second of the two patents to Kountz the temperature along the discharge line of the evaporator as well as the temperature within the space being air conditioned are both measured. An electromechanically controlled valve is included in series with the refrigeration circuit between the condensor and the evaporator and serves to control the flow of refrigerant through the evaporator.
The patent to Usami discloses a refrigeration control system for controlling an expansion valve in response to the temperature and pressure of the refrigerant discharged out of the evaporator. The patent to Schulz et al discloses a refrigeration system with a control mechanism designed to respond to variations in load conditions within the refrigeration system and to provide control signals for compensating for overlaod conditions arising during such operation. An electrically controlled valve controls the flow of refrigerant to the expansion valve.